Such a handheld power tool, configured as an ultrasonic oscillator, including a drive unit for the oscillating drive of an associated insertion tool is known from the related art. The drive unit includes an oscillating excitation actuator. Furthermore, the power tool is provided with an electronics unit for the controlled energy supply of the drive unit. The electronics unit includes an inverter, a transformer, and a measuring circuit. The inverter is configured to generate a primary-side transformer voltage and a primary-side transformer current of the transformer. The transformer is configured to transform the primary-side transformer voltage and the primary-side transformer current into an application-specific supply voltage and a supply current for the drive unit. In addition, a controller is associated with the measuring circuit, which is configured to generate at least one control signal for the inverter from a predefined setpoint value and the measured value detected by the measuring circuit. The measuring circuit is situated on the secondary side in relation to the transformer, an energy transmission for the drive unit taking place on the secondary side via friction rings.